GRADUAL PROPAGATION OF ATTRACTION. 353 
- The applause of the scientific world did not prevent 
the immortal author of the Principia from hearing some 
persons refer the principle of gravitation to the class of 
occult qualities. ‘This circumstance induced Newton and 
his most devoted followers to abandon the reserve which 
they had hitherto considered it their duty to maintain. 
Those persons were then charged with ignorance who 
regarded attraction as an essential property of matter, as 
the mysterious indication of a sort of charm; who sup- 
posed that two bodies may act upon each other without 
the intervention of a third body. This force was then 
either the result of the tendency of an ethereal fluid to 
move from the free regions of space, where its density is 
a maximum, towards the planetary bodies around which 
there exists a greater degree of rarefaction, or the conse- 
quence of the impulsive force of some fluid medium. 
Newton never expressed a definitive opinion respect- 
ing the origin of the impulse which occasioned the attrac- 
tive force of matter, at least in our solar system. But 
we have strong reasons for supposing, in the present 
day, that in using the word impulse, the great geometer 
was thinking of the systematic ideas of Varignon and 
Fatio de Duillier, subsequently reinvented and perfected 
by Lesage: these ideas, in effect, had been communi- 
eated to him before they were published to the world. 
According to Lesage, there are, in the regions of 
space, bodies moving in every possible direction, and 
with excessive rapidity. The author applied to these 
the name of ultra-mundane corpuscles. Their totality 
constituted the gravitative fluid, if indeed, the designa- 
tion of a fluid be applicable to an assemblage of particles 
having no mutual connexion. 
A single body placed in the midst of such an ocean of 
